1. Field of the Invention
The present invention relates to an electric vehicle, such as an in-wheel motor vehicle, that is equipped with motor(s) to drive wheels and that may be battery-powered or fuel cell-powered.
2. Description of Related Art
An electric vehicle may experience degradation in performance or malfunctions of a motor serving as a drive for the vehicle. This can significantly affect the travel performance or travel safety. In particular, a battery-powered electric vehicle may include a drive system with an IPM (e.g., Interior Permanent Magnet synchronous motor). Such an IPM may include a neodymium magnet to provide a highly efficient performance, thus increasing the maximum travel range that is possible with a limited battery capacity.
In the past, an in-wheel motor drive system has been proposed in which the temperature of components such as a motor may be measured and monitored for overload, with features to limit a drive current in/to the motor or a rotational frequency of the motor according to the temperature measurements, in order to ensure reliability of the system (see the Patent Document 3 listed below).    [Patent Document 1] JP Laid-open Patent Publication No. 2006-258289    [Patent Document 2] JP Laid-open Patent Publication No. 2004-328819    [Patent Document 3] JP Laid-open Patent Publication No. 2008-168790